Various mutant strains of rice have been produced in the past. These include mutant strains where lesion-like necrotic spots are formed on the leaf in connection with the growth of the rice (FIG. 1)(Rice Genetics Newsletter 12: 9-153 (1995)). This lesion formation occurs in these mutant strains under high temperature and strong light, thereby suggesting a relationship between the mutant genes and avoidance of damage by light or heat (Fuse T. et al., Physiol. Plant 89: 799-804 (1993)). On the other hand, these genes are also postulated to be related to hypersensitivity reaction in plant cells and resulting cell death, because some plants that form lesions become resistant to infections from pathogenic microorganisms (Kawasaki T. and Shimamoto K., Cell Engineering Supplement “Plant Cell Engineering Series 8: Disease Resistance of Plants at Molecular Level” pp. 124-130 (1997)).
Therefore, identification of this mutant gene in these mutant strains along with the isolation of the corresponding wild type gene may enable suppression of lesion formation and an increased resistance to stress, such as light and heat, in rice plant by introducing the gene to arbitrary cultivars via transformation methods.
Hence, there was a need in the art to identify the mutant gene in these mutant strains and also to isolate the corresponding wild type gene.